If you visit https://m.rightmove.co.uk/ the buttons do not render cleanly. Having a look at their CSS they have a number of webkit tags in there. Mobile CSS found at https://m.rightmove.co.uk/rightmove/css/rightmove.css
Reproducible. Feel free to send the admin an email :-)
Seems sorted - there's blurb about "our new mobile site" on the site, and the CSS URL above is now 404. Most importantly, I see no obvious visual problems..